1. Field of the Invention
The present invention relates to a catalyst for dehydrogenation of alkyl-aromatic hydrocarbons, to a method for producing it, and to a method of using it for producing vinyl-aromatic hydrocarbons.
2. Description of the Related Art
Heretofore, vinyl-aromatic hydrocarbons such as styrene have been produced through dehydrogenation of alkyl-aromatic hydrocarbons in the presence of a catalyst, for which generally used is an iron oxide-type catalyst as the catalyst (catalyst for dehydrogenation).
Up to now, various attempts have been made for improving the capabilities of the catalyst for dehydrogenation, for example, by adding thereto various catalyst components thereby to enhance the dehydrogenation activity of the catalyst and to prolong the life thereof. In addition, known are methods of pre-treating the catalyst for improving its capabilities.
Regarding these, we, the present applicant have disclosed a catalyst for dehydrogenation in Japanese Patent Laid-Open No. 178340/1995, which is produced by reducing an iron oxide-type catalyst that comprises iron oxide and potassium oxide added thereto, with hydrogen at a temperature falling between 350 and 600.degree. C.
The catalyst is favorable to production of vinyl-aromatic hydrocarbons, as its initial activity is high and its life is long. However, it has become known that the catalyst generates heat when exposed to air and therefore must be carefully handled so as to evade its exposure to air when filled into reactors.
The present invention is to solve the problems in the related art as above, and its object is to provide a catalyst for dehydrogenation of alkyl-aromatic hydrocarbons, which has high activity and good selectivity for the intended dehydrogenation and has a long life and which can be handled with no difficulty, and also to provide a method for producing it.
Another object of the invention is to provide a method of using the catalyst for producing vinyl-aromatic compounds, in which the catalyst exhibits high activity and good selectivity while maintaining its capabilities for a long period of time and can be handled with no difficulty.